Public awareness of emerging infectious diseases and that infectious diseases continue to be the leading cause of morbidity and mortality worldwide has fostered a need to develop better means for prevention and treatment. The evidence that most infectious agents cause disease by colonization of or penetration through mucosal surfaces has prompted novel vaccination strategies that would lead to increased protection of the mucosae as well as surfaces bathe by mucosal secretion, e.g., teeth. Secretory IgA antibodies in saliva are important in protection against oral diseases, including Streptococcus mutans-induced dental caries, and are induced following stimulation of the common mucosal immune system (CMIS). However, little information in known about the human CMIS, especially with respect to salivary IgA responses. The overall goals of this grant is to evaluate compartmentalization within the human CMIS, especially with respect to the salivary IgA response, and to develop a human caries vaccine. The purpose of the present studies is to establish the effectiveness of the intranasal (IN) route of immunization for inducing human salivary IgA responses protective against infection with S. mutans. Specifically, we will: 1) Determine the immunization regimen for the effective induction of human salivary IgA responses after IN immunization of S. mutans antigens and mucosal adjuvants. The recombinant (r) S. mutans antigens to be used are the saliva-binding region (SBR) of the adhesin AgI/II and the catalytic domain (CAT) and glucan-binding domain (GLU) of glucosyltransferase. The adjuvants to be used are the B subunit of cholera toxin (rCTB) and monophosphoryl lipid A (MPL). Adult volunteers will be used in this aspect of the study. The quality and quantity of antibody in saliva, nasal wash, and serum and of circulating antibody-secreting cells will be measured at various times up to 6 months after IN immunization with each antigen alone, antigen and an adjuvant, or a combination of antigens and an adjuvant. The oral microflora will be assessed for the number of S. mutans/total streptococci. These results should determine the effectiveness of IN immunization with S. mutans antigens in inducing salivary IgA responses, the usefulness of adjuvants in promoting the response, and whether the response was protective. 2) Determine the longevity of the human salivary IgA response after IN immunization and evaluate memory in the CMIS in terms of salivary IgA responses after subsequent IN immunization. The immune responses in serum and secretion from adult subjects used in aim 1) will be followed to evaluate the duration of the response. When the response wanes, these subjects will be boosted with the original vaccine and immunologic and microbiologic parameters will be measured to establish the effectiveness of the immunization regimen for inducing prolonged salivary responses and to learn more about memory in the human CMIS. 3) Determine the effect of age on human salivary IgA responses after IN immunization with S. mutans antigens and mucosal adjuvants. Since dental caries is a childhood disease, it is important to learn if the information we are obtaining in adults regarding the human CMIS also applies to children. In this portion of the study, children will be immunized by the IN route with antigen alone or antigen with an adjuvant. By analysis over time of antibody activity in saliva, nasal wash, and serum, we will be able to define similarities/differences in the CMIS of children and adults. By monitoring the oral microflora, we will be able to tell if the induced response was effective in reducing the level of S. mutans and in preventing the colonization by S. mutans of erupting molars. The results of this study should establish the effectiveness of the IN route of immunization, the suitability of the rSBR, rCAT and rGLU proteins of S. mutans for a combination vaccine, and the benefit of a mucosal adjuvant (CTB or MPL) for inducing a human salivary response which affords immune protection against S. mutans infection. This study will provide valuable information on the human CMIS which will help in the development of mucosal vaccines and bring us closer to establishing a human caries vaccine.